This invention relates generally to improvements in backshoe dies of the type used in tube bender machines for bending metal tubing or the like to a selected configuration, wherein such bent tubing may be used, for example, in vehicular exhaust and tailpipe systems, etc. More particularly, this invention relates to improved backshoe dies designed to accommodate versatile machine operation in bending metal tubing, while requiring a significantly reduced number of costly tooling or die components for the machine.
Tube bender machines in general are relatively well known in the art for use in bending metal tubing to a selected configuration. Such tube bender machines are commonly used by automotive vehicle repair shops to shape a length of metal tubing in a customized fashion for use in a vehicle exhaust or tailpipe system. A typical tube bender machine includes a bending die carried by a hydraulic ram for advancement into bending engagement with a length of metal tubing supported by a pair of backshoe dies mounted respectively on an outwardly pivoting pair of back gates. The bending die has a convexly curved, typically semicircularly shaped bending die face which is advanced along a line extending between the pivot axes of the back gates. As the bending die pushes into the supported metal tube, the back gates with their backshoe dies react by pivoting outwardly in unison and in opposite directions away from the bending die. This combination of bending die and back gate pivoting motion cooperates to bend the metal tube through a selected angle, in accordance with the advancement stroke length of the bending die. Importantly, the bending die face and complementary die faces of the backshoe dies define a channel of generally circular cross section of a diametric size closely matching the size of metal tube being bent by the machine.
One commercial example of a tube bender machine of this general type is marketed under the trademark BLUE BOY, by American Machine & Hydraulics, Inc., of Thousand Oaks, Calif. See also U.S. Pat. No. 3,388,574.
While tube bender machines of the general type described above have experienced significant commercial use, a variety of disadvantages limit overall machine versatility and the speed at which a metal tube can be bent at several places to a selected configuration. More specifically, in metal tubes used for vehicle exhaust systems, multiple bends in the tube are frequently required at relatively closely spaced positions. Accordingly, it is common for one bend to be formed in the metal tube, followed by tube advancement a short distance along the backshoe dies and formation of a subsequent bend in the tube. However, the previously made bend is often sufficiently close to the succeeding bend such that the previous bend does not clear the backshoe dies and thus interferes with secure seating of the tube in the backshoe dies. In the past, this interference problem has been addressed by replacing the interfering backshoe die with a shorter backshoe die component, typically referred to as a three-quarter or one-half backshoe die depending upon component length. Unfortunately, this approach requires the machine owner to purchase a set of full and partial tooling components to fit both back gates, thereby significantly increasing overall machine cost and weight as well as the number of parts which must be organized and maintained by the machine operator. Significant operator time can be absorbed in locating and changing the backshoe die components between each formed bend.
In addition, it is well known that vehicle exhaust systems utilize metal tube of a wide range of different standard diametric sizes. Accordingly, to provide a full service tube bending capability, the machine owner is required to purchase and maintain a separate full set of backshoe die components for both back gates for each different diametric size of metal tubing, wherein each backshoe die set is usable to bend L metal tubing of a single diametric size. Once again, the total number of costly tooling components undesirably increases machine cost and enhances the likelihood of operational delays due to loss or misplacement of a single tooling die component.
There exists, therefore, a significant need for improvements in backshoe dies for use in a tube bender machine, wherein the total number of required tooling die components is significally reduced, and further wherein the tooling die components are designed for use with metal tube of more than one diametric size. The present invention fulfills these needs and provides further related advantages.